Make isVectorClearMaskLegal's operand list const.

llvm-svn: 49446
diff --git a/llvm/lib/Target/X86/X86ISelLowering.h b/llvm/lib/Target/X86/X86ISelLowering.h
index e7cef08..d809950 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.h
+++ b/llvm/lib/Target/X86/X86ISelLowering.h
@@ -420,7 +420,7 @@
     /// used by Targets can use this to indicate if there is a suitable
     /// VECTOR_SHUFFLE that can be used to replace a VAND with a constant
     /// pool entry.
-    virtual bool isVectorClearMaskLegal(std::vector<SDOperand> &BVOps,
+    virtual bool isVectorClearMaskLegal(const std::vector<SDOperand> &BVOps,
                                         MVT::ValueType EVT,
                                         SelectionDAG &DAG) const;